Spherical tank shell



Feb. 7, 1950 J. o. JACKSON 2,495,626

SPHERICAL TANK SHELL Filed July 13, 1946 2 Sheets-Sheet 1 5 ATTORN EYSFeb. 7, 1950 .J. o. JACKSON 2,496,626

SPHERICAL TANK SHELL Filed July 13, 1946 2 Sheets-Sheet 2 INVENTOR My(OZ/7 4 JL-Jm/ hm jh e g b & HIS ATTORNEYS Patented Feb. 7, 1950 ISPHERICAL TANK SHELL James 0. Jackson, Grafton, Pa., assignor toPittsburgh-Des Moines Company, a corporation of Pennsylvania ApplicationJuly 13, 1946, Serial No. 683,382

13 Claims. (01. 220-1) 1 This invention relates to spherical tankshells. particularly to welded spherical metallic tank shells used forthe storage of gases or liquids under pressure, and to methods of makingsuch spherical shells.

Spherical tank shells in the past have been constructed from metal platematerial which has been cut into various shapes in the shop, then dishedto the curvature desired to form spherical sections. These sections havethen been welded or riveted together to form the spherical tank shells.

Some tank shells have been formed of plate sections such as disclosed inUnited States Patent 2,337,049. These sections are sometimes referred toas orange peel sections, the curved edges of which extend in thedirection of circles of longitude on the earth's surface.

Where the shell to be produced was large, circular plates, referred toas saucers, were generally used at the two poles of the shell, and whensuch saucers were used the body of the shell between such saucerscomprised several rows or courses of I arranging spherically dishedplates on the six sides of an imaginary cube circumscribed by suchspherical shell as disclosed in United States Pat-' ent 1,953,949.

The cube method has the advantage that the flat plates from which thesix spherical sections are formed are more nearly rectangular than theorange peel plate sections and therefore involve less trimming loss thanis inherent in the orange peel method. The cube method was used inmaking riveted spherical tank shells, but with the developments inelectric arc welding, and the trend toward welded tanks, the cube methodlost favor because of th unavoidable shrinkage stresses and distortionsencountered in making a welded spherical shell by such method. Theseshrinkage and distortion stresses are due to the 4 of the shell;

arrangement of the plate sections, which prevents When employing the"orange peel" method, in making a spherical shell, the plate sectionsmay be sequentially welded together around the circumference of theshell, thus permitting each shell part to shrink to a smaller sizewithout restraint.

An object of this invention is to produce an improved welded sphericaltank shell.

Another object is to provide an improved method of making weldedspherical tank shells;

Another object is to provide a method of making welded spherical tankshells which avoids much of the waste and scrap loss inherent in theorange peel method, and avoids objectionable shrinkage stresses anddistortions inherent in welded shells made 'by the cubef method.

A still further object is to provide a method of producing sphericaltank shells from rectangular plate-like material with but a minimumamount of scrap or waste material.

These and other objects which will be apparent to those skilled in theart of making spherical tank shells, I attain by the structure andmethod after the units of Fig. 1. The units are separated,

have their sides curved and are of a form which can be used in carryingout the method of this invention in forming a spherical tank shell;

Figs. 3 and 4 illustrate one way of cutting a rectangular plate, thentransposing and welding together the cut parts to form a straight-sidedparallelogrammic unit;

Fig. 5 illustrates a parallelogrammic unit'such as disclosed in Fig. 2,formed from fiat plate material in accordance with the disclosures ofFigs. 3 and 4;

Figs. 6 and 7 disclose one way of forming parallelogrammic units iorlarge tank shells. Each of these units comprises two rectangularplateswhich are diagonally cut and transposed;

Fig. 8 is a view similar to Fig. '7 after the 'four parts of theparallelogrammic unit of Fig. 7 have been trimmed, ready to be dished tothe contour Fig. 9 is a top plan view of a spherical shell constructedfrom five parallelogrammic units in accordance with this invention;

Fig. 10 is a view in side elevation of the tank shell in Fig. 9;

Fig. 11 is a sectional view of such tank shell taken on line XIXI ofFig. 10; and

Fig. 12 is a view similar to Fig. 9 but includes a relatively smallcircular plate section at at least one pole of the shell.

It has long been known that a hollow shellhaving the form of a regularconvex icosahedron can be constructed from five similar pieces of sheetmaterial, each having the form of a parallelogram, whose long sides areeach equal in length to two sides of one of the twenty regulartriangular faces of such icosahedron and whose short sides are eachequal in length to one such side. The area of each such parallelogrammicpiece, therefore, equals the combined areas of four of the twentyregular faces of the icosahedron.

Since such icosahedron can be circumscribed by a sphere that touches allof the vertices of all of its twenty triangular faces, it is possible todivide the entire surface of such sphere into twenty abuttingequilateral spherical triangles.

It therefore follows that a spherical tank shell can be constructed fromtwenty similar equilateral triangular sections of plate-like materialthat are dished to the contour of the shell to be produced and whichafter dishing, have their edges trimmed so that they will interfit toform the complete spherical shell. The dishing and trimming operationsconvert the equilateral triangular sections into equilateral sphericaltriangular shell sections. Instead of dishing and then trimming, theflat plate-like material can be divided into twenty pieces each havingthe outline of a development of one of the twenty similar equilateraltriangular spherical shell sections.

Welded spherical tank shells can be fabricated from such sphericaltriangular sections, but it would involve an excessive amount ofwelding, and, unless the spherical triangular sections were weldedtogether in a manner which permits free shrinkage of each such section,the completed shells would contain excessive weld shrinkage stresses anddistortions.

I have found that the welding can be materially reduced, weld shrinkagestresses and distortions reduced to a negligible quantity andrectangular plate-like material can be used with but a minimum of wasteor scrap loss, if the twenty equilateral spherical triangular shellsections into which a spherical shell surface is capable of beingdivided are grouped into five similar units, each of which in the mainhas the form of a parallelogram, but has curved sides or edges asdisclosed in Figs. 2, 5 and 8.

In what I now consider the preferred manner of carrying out themethod-oi this invention, I divide the spherical shellto be producedinto twenty similar equilateral spherical triangles, or sphericaltriangular shell sections. I arrange these triangular sections in fivesimilar groups each of which forms a unit which embraces four of thetwenty triangles making up the complete spherical shell. The fourtriangles of each such group or unit are arranged side by side inabutting but alternately reversed relation, to form,

when such triangles are developed, a figure having an outline which inthe main is that of a parallelogram, except that each of the long sidesof each such figure comprises two curved sides of two of the fourspherical triangles when developed, while the short sldes each compriseone such curved side, as disclosed in Figs. 2 and 5.

The five parallelogrammic units are then dished to form spherical shellsections having the contour of the spherical shell to be produced. Thesespherical sections are secured together in side by side relation,preferably by welding, to produce the complete spherical tank shell withthe extreme ends of the live spherical sections meeting at oppositepoles of the spherical shell as disclosed in Figs. 9 to 11 inclusive.

In some spherical tanks, it may be desirable to place a relatively smallcircular plate section at one or both poles of the shell as shown inFig. 12 for the purpose of accommodating manholes or other tankelements. When this is done, the five spherical shell units whichnormally extend from pole to pole and meet at such poles will eitherhave to have one or both ends, as the case may be, trimmed toaccommodate such circular plate section or sections, or may have one orboth ends purposely formed to accommodate such circular section orsections to which they are united as by welding. When a circular platesection is used at a pole of the spherical shell, the end triangle ofthe four into which each spherical shell unit is divisible, will be moreor less truncated or minus its extreme outer vertex. In such case, thespherical shell units will not extend exactly, but substantially frompole to pole.

If the tank shell to be produced is relatively small, the five sphericalsections can be assembled in position and temporarily connectedtogether, as by tack welding after which the shell sections arepermanently welded together in a fluid-tight manner. In this weldingprocedure, two adjacent sections are first welded together throughoutthe full extent of their abutting edges. Welding of the other shellsections to these may then proceed in either direction around thecircumference of the shell, and as long as each weld seam betweenadjacent shell sections is completed throughout its full length beforewelding of the next adjacent seam has started, the shell sections canshrink without restraint.

If the tank shell is relatively small, all five units may be cut fromone long flat plate, or each of the five units can be formed from asingle small fiat plate by diagonal cutting, transposing and welding, asdisclosed in Figs. 3, 4 and 5. As shown in Figs. 2 and 5, each of theseunits is given an outline which in the main is that of a parallelogram,but has the exterior edges or sides of the four triangles embraced ineach such unit, slightly curved as they appear when the sphericaltriangles aredeveloped. They then appear substantially as shown in Figs.2 and 5. The curved edges or sides allow for the dishing operation whichtransforms them into spherical sections.

The dimensions of each of the five parallelogrammic units will dependupon the size of the spherical tank shell to be produced.

When the tank shell is to be relatively large, eachof theparallelogrammic units may be a multi-part unit made from any desirednumber of pieces of rectangular plate material without producingexcessive scrap or waste material. Fig, 8 discloses such a multi-partunit having four parts and such unit may be made from two rectangularplates by following the procedure depicted in Figs. 6 and 7. In'thisprocedure, each of the two rectangular plates is cut diagonally as shownin Fig. 6 to form one long and one short plate. These four plates arethen transposed and arranged as disclosed in Fig. '7 to form suchmultipart parallelogrammic unit. Each of the parts making up such unitmay then be trimmed as shown in Fig. 8 or they may be dished and thentrimmed. I prefer to trim them before dishing,

since the procedure is simpler. Some scrap loss will be produced byfollowing either procedure, but the amount will be less than producedwhen using the orange peel method in constructing a spherical shell.

By way of example, in constructing a spherical tank shell 28'9/2" insidediameter, utilizing the orange peel method, it is necessary to purchase3670 square feet of steel plate material.

Such a tank shell requires 590 lineal feet of seam welding. Inconstructing, by the method of this invention, a spherical tank shell ofthe same diameter, I need to purchase but 2900 square feet of steelplate material and the seam welding amounts to but 476.5 lineal feet.The saving in steel plate material for the spherical shell utilizing themethod of this invention as against the "orange peel method, therefore,amounts to 19%, while the saving in the welding procedure amounts to21%.

In constructing large spherical tank shells from multi-part units, theseveral parts of each such unit will be trimmed and dished in the shop,shipped to the point of erection and assembled and welded in the field.It is, therefore, advisable to so mark each part of the diiferentmulti-part units that its proper position within the unit of which itforms a part can be readily ascertained and maintained.

In making welded spherical tank shells, the individual spherical shellunits making up such shells may overlap as in riveted spherical tankshells. In order to make these lap joints, either welded or riveted, theindividual spherical shell units will be made oversize and the centerlines of the overlaps, whether the tank shell is lap welded or riveted,will define five similar spherical triangular shell units. Each of thefive units thus defined will be divisible into four equilateraltriangular shell sections arranged side by side in alternately reversedabutting relation.

When lap joints are used, one or both units of any adjacent pair ofunits may be oversize in order to provide for the lap. Whether such lapis all provided in one of a pair of adjacent units or in both suchadjacent units, the center line of the lap-when both units are oversizeor the outline of the normal unit when only one unit is oversize-will beconsidered the outline of each unit of the adjacent pair and suchoutline will be divisible into four equilateral spherical triangularshell units of the same size arranged side by side in alternatelyreversed abutting relation.

In addition to complete spherical tank shells, the method of myinvention is valuable and of advantage in the making of partialspherical tank shells, such for example as half, or hemispherical tankshells or tank bottom portions.

A hemispherical tank shell embodying this invention may be made inseveral ways. One way is to in effect prepare the spherical shell unitsas though a complete spherical shellwere to be made, then out each shellunit transversely into halves and construct two hemispherical tankspherical shell section made in the form ofa spherical isoscelestriangle having two sides each equal length to one of the sides ofthefour equilateral triangles of the adjacent units and each hailing itsthird side equal in length to half the circumference of the shell minusthe length of one side of such equilateral triangles.

Still another way is to lay out two regular spherical shell units, eachdivisible into four equilateral spherical triangular shell sections ofthe same size arranged in reversed abutting relation. Then lay out thetwo shell sections made in the form of spherical isosceles trianglesabove referred to, one for each side of the double unit. Then placethese in position in the layout. This will form two spherical units,each having .a, spherical surface equalling the spherical surface of onehalf of the hemispherical shell, or five of the regular twentyequilateral triangular sections into which the complete spherical shellis divisible.

What I claim is:

l. A hollow spherical tank shell comprising five similar spherical shellunits connected to gether in a fluid-tight manner and eachbeingdivisible into four equilateral spherical triangular sections ofthe same size, arranged side by side in alternately reversed abuttingrelation and which take in the entire area of such unit.

2. A hollow spherical shell comprising five spherical shell unitsconnected together'in a fluid tight manner and in side by side relation,each such unit extending substantially from one pole to the oppositepole of such shell and ach being divisible into four substantiallycomplete equilat eral spherical triangular shell sections of the samesize arranged side by side, in alternately reversed abutting relationand whichtake in the entire area of such spherical shell unit. I

3. A spherical shell section for use as a unit in making a spherical orhemispherical Etank shell, such unit having an overall lengthsubstantially equalling one half the circumference of the tank shell orpart to be produced and being divisible into four equilateral sphericaltriangular shell sections of the same size arranged side by side inalternately reversed abutting relation and which take in the entire areaof such-shell unit.

. such shell to the opposite pole thereof, each such unit beingdivisible into four substantially complete equilateral sphericaltriangular fiections arranged side by side, in alternately reifersedabutting relation and which take in the entire area of such unit, suchmulti-part units and the parts thereof being welded together in afluid-tight manner.

5. A hemispherical tank shell comprising two units each having anoverall length substantially equalling one half thecircumference of thetank shell and being divisible into four equilateral sphericaltriangular shell sections of the same size arranged side by side inalternately reversed abutting relation, and two spherical isoscelestriangular shell sections each having two of its sides equal in lengthto one side of such equilateral triangular sections and its third sideequal in length to one half the circumference of the shell minus thelength of one side of such equilateral triangular sections; such shellsections into which each unit is divisible embracing the entire area ofsuch unit.

6. A inulti-part parallelogrammic unit for use in making a spherical orhemispherical tank shell, such unit having an overall lengthsubstantially equalling one-half the circumference of the tank shell orpart to be produced, comprising a number of spherical shell sectionsconnected together in a fluid-tight manner, being divisible into fourequilateral spherical triangular shell sections of the same sizearranged side by side in alternately reversed abutting relation andtaking in the entire area of such unit.

7. A multi-part parallelogrammic unit for use in making a spherical orhemispherical tank shell, such unit having an overall lengthsubstantially equalling one-half the circumference of the tank shell orpart to be produced, comprising a number of spherical shell sectionswelded together in a fiuid-tight manner, being divisible into fourequilateral spherical triangular shell sections of the same sizearranged side by side in alternately reversed abutting relation andtaking in the entire area of such unit.

8. A multi-part parallelogrammic unit for use in making a spherical orhemispherical tank shell, such unit having an overall lengthsubstantially equalling one-half the circumference of the tank shell orpart to be produced, comprising a number of spherical shell sectionsarranged in overlapping relation, riveted together in a fluid-tightmanner, being divisible into four equilateral spherical triangular shellsections of the same size arranged side by side in alternately reversedabutting relation and taking in the entire area of such unit.

9. A multi-part parallelogrammic unit for use in making a spherical orhemispherical tank shell, such unit having an overall lengthsubstantially equalling one-half the circumference of the tank shell orpart to be produced, comprising a number of spherical shell sectionsarranged in overlapping relation, connected together in a fluid-tightmanner, being divisible into four equilateral spherical triangular shellsections of the same size arranged side by side in alternately reversedabutting relation and taking in the entire area of such unit.

10. A hollow spherical shell comprising five spherical shell unitsconnected together in a fiuidtight manner and in side by side relation,each such unit extending substantially from one pole to the oppositepole of such shell and each being divisible into four substantiallycomplete equilateral spherical triangular shell sections of the samesize arranged side by side, in alternately reversed abutting relationand which take in the entire area of such spherical shell unit, suchshell having a circular plate section located at at least one of itspoles and having substantially one-fifth of its peripheral edgeconnected in a fluid-tight manner to each of such spherical shell units.

" 11. A hollow spherical shell comprising five spherical shell unitsconnected together in a fluidtight manner and in side by side relation,each such unit extending substantially from one pole to the oppositepole of such shell and each being divisible into four substantiallycomplete equilateral spherical triangular shell sections oi the samesize arranged side by side, in alternately reversed abutting relationand which take in the entire area of such spherical shell unit, suchshell having a circular plate section located at each of its poles, eachsuch circular plate section having substantially one-fifth of itsperipheral edge connected in a fluid-tight manner to each of suchspherical shell units.

12. A hollow spherical tank shell comprising five similar overlappingspherical shell units connected together in a fluid-tight manner and inwhich the center lines of the overlaps around each such unit define afigure which is divisible into four equilateral spherical triangularsections of the same size arranged side by side in alternately reversedabutting relation and which take in the entire area of such figure.

13. A hollow spherical shell comprising five spherical shell unitsconnected together in a fluidtight manner and in overlapping relation,each such unit extending substantially from one pole to the oppositepole of such shell and in which the center lines of the overlaps definefive figures each of which is divisible into four substantially completeequilateral spherical triangular shell sections of the same sizearranged side by side, in

alternately reversed abutting relation and which take in the entire areaof such spherical shell unit.

JAMES O. JACKSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

